DETECTION OF EPITHELIAL CANCER-CELLS IN PERIPHERAL-BLOOD BY REVERSE-TRANSCRIPTASE POLYMERASE CHAIN-REACTION

Circulating cancer cells in the blood play a central role in the metas tatic process. Their numbers can be very small and techniques for thei r detection need to be both sensitive and specific. Polymerase chain r eaction (PCR) has been successfully used to detect small numbers of tu mour cells in haematological cancers, in which abnormalities in DNA ar e sufficiently consistent to make this possible. For most solid tumour s this is not yet feasible. However, we have found that reverse transc riptase (RT)-PCR for tissue-specific gene expression is a useful techn ique for identifying small numbers of circulating cells in melanoma an d neuroblastoma patients. In this report we describe detection of colo n carcinoma cells by RT-PCR using CK 20 mRNA as a marker. Unlike other cytokeratin genes examined (CK 8 and CK 19), CK 20 was not transcribe d in normal haematopoietic cells. This suggests a role for RT-PCR in t he detection of colon carcinoma metastasis in blood and bone marrow, u sing CK 20 as the target gene. Future analysis of clinical material wi ll determine the clinical significance of this technique.